Sectioned multiple-step pulley transmission

Abstract

A pulley for a transmission system, including a central rotatable hub having a circumference; and a plurality of adjoining identical pulley segments rotatably mounted about the central hub circumference, wherein the adjoining pulley segments form an approximately circular stepped pulley shape and each of the pulley segments includes two sections providing two curved shelf surfaces for engaging a flexible drive member, each shelf having a different radius, forming higher and lower steps, and further wherein each of the pulley segments are independently rotatable about a radial axis with respect to the central hub.

What is claimed as invention is: 
     
       1. A multiple step pulley for variable power transmission, comprising:
 a central hub which rotates about a hub axis, said central hub having a hub shell; 
 a plurality of operationally identical pulley segments rotatingly disposed on said hub shell and configured with pulley sections having at least first and second shelf portions which collectively align to engage a flexible drive member in a drive portion of the multiple step pulley as said central hub rotates under a force applied by the flexible drive member or at it applies force to a flexible drive member, and to disengage from the flexible drive member in a shift window portion of each rotation of said central hub about said hub axis, said pulley segments further configured with elements that engage a shifting mechanism; and 
 a shifting mechanism operatively connected to said central hub and configured to selectively engage said each of pulley segments in said shift window portion; 
 wherein said pulley segments rotate about a pulley segment axis substantially radial to said hub axis; and 
 wherein said first and second shelf portions each define an arc having a different radius from said hub axis. 
 
     
     
       2. The multiple step pulley of  claim 1 , wherein each of said first and second shelf sections comprises an arc that combine and align with all other of the respective first and second shelf portions to form a substantially circular multisectioned pulley with spacing between each of said pulley sections to permit rotation of each of said pulley sections in said shift window about said pulley section axes. 
     
     
       3. The multiple step pulley of  claim 1 , wherein said pulley sections have at least first and second shelves. 
     
     
       4. The multiple step pulley of  claim 3 , wherein said at least first and second shelves of each of said pulley sections are in a side-by-side relationship straddling said pulley segment axis. 
     
     
       5. The multiple step pulley of  claim 1 , wherein said shifting mechanism comprises a shift ring, a stationary partial ring gear, and a shift wire with a selector tooth, and said pulley segments include a pinion gear and shift hooks configured to engage said selector tooth when in a shift configuration. 
     
     
       6. The multiple step pulley of  claim 5 , wherein each pulley segment further includes at least one spring-biased pawl that engages a detent disposed in said hub to prevent rotation of a pulley segment beyond that needed for a shift from one shelf to another shelf and which stabilizes said pulley segment between shifts. 
     
     
       7. The multiple step pulley of  claim 1 , wherein said central hub is configured with an axial opening adapted to accept a cassette body. 
     
     
       8. The multiple step pulley of  claim 6  configured for incorporation into a bicycle drive system. 
     
     
       9. The multiple step pulley of  claim 7 , wherein said multiple step pulley is configured for incorporation into a rear internal gear hub. 
     
     
       10. The multiple step pulley of  claim 1 , wherein each of said pulley segments comprises an assembly having said pulley sections exposed for operational engagement with a flexible drive member and shifting elements disposed in said hub interior for selective engagement with said shifting mechanism. 
     
     
       11. The multiple step pulley of  claim 10 , wherein said shifting elements of said pulley segments include pinion gears having symmetrically opposing sets of gear teeth and shift hooks disposed therebetween. 
     
     
       12. The multiple step pulley of  claim 11 , wherein said shifting mechanism includes a stationary partial ring gear and a shift ring with a shift wire having a selector tooth which engages said shift hook to initiate a shift event when a shift is selected, thereby bringing one of said set of opposing sets of gear teeth on said pulley segments into mesh engagement with said stationary partial ring gear. 
     
     
       13. The multiple step pulley of  claim 1 , further including a variable force tensioner to maintain a substantially constant tension on the flexible drive member during operation, including during shift events. 
     
     
       14. The multiple step pulley of  claim 13 , wherein said variable force tensioner includes an idler wheel urged against the flexible drive member with a variable spring force mechanism. 
     
     
       15. The multiple step pulley of  claim 14 , wherein said idler wheel engages said flexible drive member proximate the end of said shift window portion. 
     
     
       16. A pulley for a transmission system, comprising;
 a central rotatable hub having a circumference; and 
 a plurality of adjoining identical pulley sections rotatably mounted about the central hub circumference, wherein the adjoining pulley segments form an approximately circular stepped pulley shape and each of said pulley segments includes two sections providing two curved shelf surfaces for engaging a flexible drive member, each shelf having a different radius, forming higher and lower steps, and further wherein each of said pulley segments are independently rotatable about a radial axis with respect to said central hub.